Rate of sea-level changes due to climate changes vary according to latitudes: namely (i) in high and middle latitudes, successive glacial, interglacial and interstadial conditions occur with significant sea-level rises, and (ii) in low latitudes, successive humid and arid conditions occur with small sea-level rises or falls. Inter-governmental Panel on Climate Change's (IPCC) projection of future sea-level rise in the high and middle latitudes of 31, 66 and 110 centimeters in 100 years for low, middle and high scenarios respectively is wrongly accepted to be applicable to the Gulf of Thailand, which is in the low latitudes, where air and seawater temperatures are already high, and therefore, an insignificant increase of temperatures is found in several large cities. Analyses of 56 years data of tides recorded at Ko Lak, Prachuap Khirikhan province and Sattahip, Chonburi province revealed that sea levels are falling slowly, which is consistent with results of Gregory (1993) who reported sea-level falls in the low latitudes and the Gulf of Thailand of 0-50 milimeters, using U.K. Meteorological Offices Coupled Ocean-atmosphere General Circulation Model. In conclusion, the sea-level in the Gulf of Thailand is found preliminarily to be falling slightly or not changing, contradicting the belief that sea-level is rising in the Gulf of Thailand at the same rate as that in the high and middle latitudes. This should be investigated in more detail in the near future.